Painting MDF

[Pete Robinson]

I want to put a black paint finish on some MDF, last time I tried this I sealed it with two coats of watered down PVA but found the edges were still like a sponge and took several top coats to achieve a decent finish and was a real pain.

Also I would ideally like to spray it in order to eliminate any possible brush marks any advice on methods and materials would be excellent.

Cheers

Pete

 

[Oryxdesign]

What sort of spray facilities do you have?

 

[Mike Wingate]

MDF primer sealer. A couple of extra coats on the edges.

 

[Pete Robinson]

its only a flat piece about 9"x31" and I was thinking about using an aerosol.

 

[Oryxdesign]

OK I think you need to paint it first with something that will penetrate and dry hard, a coat of Rustins Plastic Coating or similar will do, thin it well. Sand off and prime and paint with car type paint it'll be fine. When you sand it you need to get back to perfectly flat so you will be sanding most of the PC off, fit the PC with a gloss roller. Do a test first to make sure the aerosol you buy is compatible with the PC or whatever you use.
Or you could drop into your local car body shop and get them to do it for you, 2K primers work fine although you do need a few coats.

Simon

 

[nicewood]

Get some Pre-Cat wood primer, treat the edges only, when dry sand well if the edges still look porous coat again and sand, finally coat the whole board and sand apply a finish of your choice. This primer is intended for spraying by gun but with care it can be brushed on also. Good luck

 

[cornucopia]

The best way to prime MDF before spraying or hand painting is to use a shellac based primer such as Zinnser BIN- b&q stock it or any dulux, crown, johnstones,leyland paint centre also stock it. you can thin it by 10% with meths which makes application easier (being shellac basd it dries super fast) Ventalate the area well and be aware of how flamable it is.

Simply apply it wait 10/15minutes knock it back with some 180 and apply your choice of paint.

 

[Pete Robinson]

Some ideas here I would never have thought of which I will have to put to the test.

Thanks All

 

[mailee]

Ok I'll add my two, hapeth here too. I am just building a MDF unit and am sealing it with Cellulose sanding sealer. I apply a 50/50 mix of sanding sealer and thinner for the first coat by brush. (This allows it to penetrate the MDF fibres deeper) I sand this with 320 grit and then apply another coat brushed on of 75/25 this time using more of the sanding sealer. (This will not penetrate as deep this time) After this is dry I wet sand it with 500 to 800 wet n dry. If you give the edges one extra coat allowing it to flash off between coats and this will seal them perfectly. After flatting with the wet n dry hold the edge up to the light and you will see how smooth it is. After this process you can then go straight on with the paint and or laquer. HTH. :wink:

 

[pren]

Just to add my 'swear-by' to the mix, I use lots of 50/50 PVA water mix on the edges. Sand this back with 120grit then cover with a flat matt emulsion. Once this has dried, sand with 180g and give the whole board (inc edges) a further coat, applied with a 4" foam/gloss roller. Sand this with 180g. If the edges still look rough, coat them again with the emulsion.

I've always found flat matt emulsion to be great for MDF. It's cheap and sands back like plaster or car body filler. 8)

With painting, I've always found a 4" gloss roller to be a pretty good way to get a decent finish if you're not set up for spraying.

 

[lemonjeff]

Bryn,
Do you use a top coat straight on the emulsion?

Jeff

 

[pren]

Yes. I've used both Eggshell and gloss over the emulsion coat and they've gone on fine.

 

[Tenko]

Now to add another two pennies worth in ....

I always use 100% PVA on the edges, it seals, soaks in and doesn't sepperate.

 

[CroppyBoy1798]

Just to add my 'swear-by' to the mix, I use lots of 50/50 PVA water mix on the edges. Sand this back with 120grit then cover with a flat matt emulsion. Once this has dried, sand with 180g and give the whole board (inc edges) a further coat, applied with a 4" foam/gloss roller. Sand this with 180g. If the edges still look rough, coat them again with the emulsion.

I've always found flat matt emulsion to be great for MDF. It's cheap and sands back like plaster or car body filler. 8)

With painting, I've always found a 4" gloss roller to be a pretty good way to get a decent finish if you're not set up for spraying.

Been using this method today, first time! Have to say seems to be working a treat so far! Like you said, the matt emulsion is like fillers on a card body, sands down to a lovely smooth surface, hell'uva lot of dust though.

I'm spraying the parts, took a little while to get a good consistant spray going, but it turned out ok. I also sealed the edged first with an MDF sealer (basicall watered down PVA!).

I'm not all that familiar with painting pren, but, when you say 'eggshell' is this a form of paint, like Satinwood, vinyl, etc. Just been looking through a few color cards here and I dont see eggshell mentioned, I know its a satin/mid sheen finish?

 

[lemonjeff]

Silk or Satin according to this http://www.paintquality.co.uk/qualitypaint/Sheens.html

Jeff.

 

[CroppyBoy1798]

Thanks Lemonjeff!